Helen Williams of Detroit held her own infant daughter close to her as she climbed the stairs Friday and placed red flowers on the growing pile. Her other two children stood by silently.

"I don't understand how someone could just leave a baby in that house," Williams said. "There are so many things that person could do than leave him like that."

Isaiah Lewis had been missing since Aug. 3, when his 20-year-old mother, Shaniqua Betty, handed him to a stranger at a bus stop about 1 a.m. and asked the man to look after him for a few minutes. She said she needed to get her purse from her boyfriend's home about three quarters of a mile away. When she returned, the stranger and the child were gone.

Police on Thursday arrested a 48-year-old man after a caller identified him from a convenience store surveillance tape shown on the evening news.

The man led them to the abandoned building in the burned out neighborhood, just five blocks from the bus stop where Betty last saw Isaiah. The boy's body was found in a second-floor bedroom under a pile of trash and debris. Broken glass, old toys and dirty diapers littered the floor of the home.

Police didn't identify the man or say what charges might be filed, but they said he likely would be arraigned Sunday in connection with Isaiah's death.

Chief Charles Wilson said he didn't know if charges would also be filed against Betty. He said a police child abuse unit would investigate.

Court records show that Betty had a history of psychological problems. A court-ordered psychological evaluation warned last year that she was "not capable of caring for or rearing a baby," the Detroit Free Press reported.

According to court records, the Oakland County Family Independence Agency repeatedly failed to provide psychological help for Betty, despite demands by juvenile court officers. FIA officials said they could not comment on the case because of client confidentiality.

Police wouldn't speculate on how Isaiah died, but Wilson said preliminary findings indicate it was shortly after he disappeared.

For nearly a week, police and the FBI searched for clues to the baby's disappearance. A Detroit radio station offered a $10,000 reward for the child's safe return, and Isaiah's distraught mother went on television begging to be reunited with her son.

The surveillance tape from a convenience store near the bus stop turned out to be the key.

Police got the tape immediately after the baby disappeared and initially thought it yielded no clues. Later, they learned the timing on the tape was off by an hour. With help from General Motors Corp., which used its computer technology to enhance the quality of the tape, investigators reviewed it again and saw the suspect.

Just after 1 a.m. on Aug. 3, the tape showed a man walking into the 24-hour Marathon Stop & Go cradling a baby wrapped in a towel. He stood at the register, adjusted the towel around the baby and paused, apparently to coo at the infant. Then he left the store.

Betty told police she was able to identify the baby as Isaiah and the man as the stranger she asked to watch him. Investigators said both she and the baby's father had been questioned during the past week about the child's disappearance and had passed lie detector tests.

Attempts to reach Betty for comment Friday were unsuccessful.

Meanwhile, members of the community, many of whom said they had been praying for Isaiah's safe return, struggled to deal with his death.

Cheryl Jackson, who lives near the house where Isaiah was found, said she thought police would find Isaiah alive after seeing the broadcast surveillance tape showing the man and the baby.

"I didn't think they would find this," said Jackson, also the mother of an infant. "I don't know how she could leave her baby like that. I wouldn't leave mine for a minute."